Hybrid Quantum Photonics Based on Artificial Atoms Placed Inside One Hole of a Photonic Crystal Cavity
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2021-08-17 |
| Journal | ACS Photonics |
| Authors | Konstantin G. Fehler, Lukas Antoniuk, Niklas Lettner, Anna P. Ovvyan, Richard Waltrich |
| Institutions | UniversitÀt Ulm, Centre National de la Recherche Scientifique |
| Citations | 21 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive SummaryâThis research demonstrates the successful integration of solid-state quantum emitters into a scalable photonic crystal cavity (PCC) platform, achieving significant performance boosts for quantum network applications.
- Hybrid Quantum Node: A high-bandwidth quantum node was realized by deterministically placing Silicon-Vacancy (SiV-) centers, hosted within nanodiamonds (NDs), inside a hole of a freestanding one-dimensional Silicon Nitride (Si3N4) PCC.
- Enhanced Photon Flux: The resulting photoluminescence (PL) intensity was enhanced by up to a factor of 14 compared to free-space emission, achieved through optimized two-mode composition, waveguiding, and Purcell enhancement.
- High Operational Bandwidth: The Purcell effect shortened the excited state lifetime of the SiV- transition to 460 ps, putting the potential operational bandwidth beyond GHz rates.
- Integration Accuracy: The approach successfully overcomes the challenge of precise positioning by utilizing AFM-based nanomanipulation to place the ND host accurately within the electric field maximum of the PCC hole.
- Scalability: The hybrid architecture leverages the advantages of a well-established Si3N4 photonics platform, making it compatible with large-scale integration into photonic integrated circuits.
- Spectral Control: Controlled coupling was demonstrated by tuning the effective cavity mode resonance via gas freezing at cryogenic temperatures, enabling time-resolved coupling to individual SiV- transitions.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| PL Enhancement Factor | Up to 14 | Factor | Compared to free-space emission. |
| Shortest Measured Lifetime (Ï) | 460 | ps | Due to Purcell effect; implies bandwidth > GHz. |
| PCC Material | Stoichiometric Si3N4 | N/A | Freestanding waveguide thickness: 200 nm. |
| Diamond Refractive Index (nDia) | 2.4 | N/A | Nanodiamond host material. |
| Si3N4 Refractive Index (nSi3N4) | â 2.0 | N/A | Refractive index contrast aids waveguiding. |
| PCC Period (a) | 265 | nm | Bragg mirror hole separation. |
| Cavity Defect Distance | 232 | nm | Distance between the two Bragg mirrors. |
| Target ZPL Wavelength (SiV-) | 740 | nm | Optimization wavelength for probe waveguide. |
| Cryogenic Operating Temperature | â 2.5 | K | Continuous flow-cryostat (Janis ST-500). |
| CW Excitation Wavelength | 710 | nm | Off-resonant pumping (Titan-Sapphire laser). |
| CW Excitation Power | â 50 | ”W | Used for PL measurements to ensure low background. |
| ND Synthesis Pressure | 8.0 | GPa | High Pressure High Temperature (HPHT) process. |
| ND Synthesis Temperature | 1450 | °C | HPHT process, short (3s) isothermal exposure. |
Key Methodologies
Section titled âKey Methodologiesâ- Nanodiamond (ND) Synthesis: SiV- containing NDs were produced via High Pressure High Temperature (HPHT) synthesis (8.0 GPa, 1450 °C, 3s exposure). The precursor mixture included naphthalene, detonation ultranano-sized diamonds, and tetrakis(trimethylsilyl)silane, targeting an initial atomic Si/C ratio of 1/100.
- PCC Fabrication: Freestanding one-dimensional PCCs were fabricated on Silicon nitride-on-insulator wafers (200 nm Si3N4 on 2 ”m SiO2).
- Lithography and Etching: Electron-beam lithography (using ma-N 2403 and PMMA resists) defined the nanophotonic circuits. Si3N4 was dry-etched (CHF3/O2 plasma). Freestanding structures were achieved by wet etching the underlying SiO2 layer using hydrofluoric acid (HF).
- Emitter Pre-characterization: Individual SiV- centers in NDs were spectrally pre-characterized on a separate substrate using a home-built confocal microscope at cryogenic temperatures.
- Deterministic Integration (Pick and Place): An AFM-based nanomanipulation procedure was used to pick up a pre-characterized ND and accurately place it into the second hole of the PCC Bragg mirror, ensuring optimal spatial overlap with the cavity mode field.
- Spectral Tuning and Stabilization: The cavity resonance frequency was controlled and tuned by cooling the PCC in a continuous flow-cryostat (â 2.5 K). Residual gas freezing onto the PCC surface altered the effective refractive index, allowing controlled spectral overlap with the SiV- transition lines.
- Optical Characterization: Measurements utilized a confocal setup (0.55 NA objective). PL enhancement was measured using a CW Titan:Sapphire laser (710 nm). Lifetime shortening was measured using a pulsed Optical Parametric Oscillator (OPO) and single photon counting modules, with spectral filtering via a commercial spectrometer (HRS-500).
Commercial Applications
Section titled âCommercial ApplicationsâThe demonstrated hybrid quantum photonics platform is crucial for developing robust, high-performance components for next-generation quantum technologies:
- Quantum Networks and Internet: Serving as high-bandwidth quantum nodes capable of mediating interaction and transferring quantum information between stationary qubits (spins) and flying qubits (photons).
- Distributed Quantum Computing: Providing efficient spin-photon interfaces necessary for entanglement distribution across remote computational modules.
- Quantum Memory: Utilizing the SiV- center in diamond, which offers exceptional spectral stability and access to long-lived, nuclear-spin quantum memories for storage and retrieval of quantum states.
- Integrated Quantum Circuits: The Si3N4 platform is highly compatible with large-scale integration, enabling the mass production of complex, on-chip photonic circuits containing multiple quantum emitters.
- Secure Communications: Enabling fundamental elements for secure key distribution and blind quantum computation protocols.
- Metrology and Sensing: Applications requiring stable, optically addressable solid-state spins, such as high-precision clock synchronization.
View Original Abstract
Spin-based quantum photonics promise to realize distributed quantum computing\nand quantum networks. The performance depends on efficient entanglement\ndistribution, where the efficiency can be boosted by means of cavity quantum\nelectrodynamics. The central challenge is the development of compact devices\nwith large spin-photon coupling rates and high operation bandwidth. Photonic\ncrystal cavities comprise strong field confinement but put high demands on\naccurate positioning of an atomic system in the mode field maximum. Color\ncenter in diamond, and in particular the negatively-charged Silicon-Vacancy\ncenter, emerged as a promising atom-like systems. Large spectral stability and\naccess to long-lived, nuclear spin memories enabled elementary demonstrations\nof quantum network nodes including memory-enhanced quantum communication. In a\nhybrid approach, we deterministically place SiV$^-$-containing nanodiamonds\ninside one hole of a one-dimensional, free-standing, Si$_3$N$_4$-based photonic\ncrystal cavity and coherently couple individual optical transitions to the\ncavity mode. We optimize the light-matter coupling by utilizing two-mode\ncomposition, waveguiding, Purcell-enhancement and cavity resonance tuning. The\nresulting photon flux is increased by more than a factor of 14 as compared to\nfree-space. The corresponding lifetime shortening to below 460 ps puts the\npotential operation bandwidth beyond GHz rates. Our results mark an important\nstep to realize quantum network nodes based on hybrid quantum photonics with\nSiV$^-$- center in nanodiamonds.\n